Electrical Power Analysers

The Dewetron power analyser product range has been optimised for high accuracy power measurement. Applications include electric and hybrid vehicle drivetrain development, renewable energy measurement and transformer testing.

Power measurement features gapless cycle by cycle detection, to ensure no blind spots. Hence, this is ideal for testing during dynamic load changes, where traditional power meters fail.

Power measurement is from 4 channels (3 phase + DC link) to 32 channels, with optional speed and torque inputs. The power analyser provides both electrical and mechanical power calculation capabilities, used to optimise performance and efficiency. Analysis features include real time efficiency mapping, DQ analysis.

The power analyser provides data transfer to a test cell controller in a range of digital formats including EtherCAT, CAN and CAN-FD.

View the sensors section on our website for Current Clamps and other accessories.

Choosing the right type of Power Analyser

As you can imagine with a large proportion of engineering activities, choosing the incorrect tool may have serious implications on the results of your measurements. The information contained below is to help visitors make a more informed decision on a power analyser which is most appropriate for their requirements.

What is Power Analysis?

Power is the rate of doing work, or the amount of energy spent per unit of time. The power of an electrical system is calculated by multiplying the measured voltage by the measured current, then integrating and dividing the result over a period of time. In order to calculate the power of an AC electrical system, the periodic time (inverse of the fundamental frequency) must be known. The term “power analysis” simply refers to the process of determining how much power is available.

What is a Power Analyser?

A  power analyser is an instrument used to measure the rate of power flow in electrical systems. The flow of power is measured in kilojoules per second (J/s) or kilowatts (kW). Electrical power is the rate at which electrical energy is moved between two places in an electrical system per unit of time.

How is Electrical Power calculated?

The method used depends on whether DC or AC power is being calculated. AC power is further broken down into three types, see below.

DC power

DC power is calculated by multiplying voltage (Volts) by current (Amps). The resultant power is measured in Watts (W). This is based on Ohm's law, and is true where the flow of current is always in the same direction.

AC power

In an alternating current (AC) circuit consisting of a source and a load, both the current and voltage are sinusoidal at the same frequency. AC power consists of active power, reactive power and apparent power.

Active power

Active power AKA real power is the amount of power that is actually consumed in an AC circuit. Active power is the instantaneous voltage multiplied by current averaged over the fundamental period. Thus to calculate active power, the fundamental frequency must also be measured.

Reactive power

The reactive power (kVAR) establishes the magnetic field in the motor that enables it to operate. It represents the amount of power that continuously bounces back and forth between the source and load meaning the power which cannot be used for effective work in an AC circuit or system. It is the difference between active and apparent power.

Apparent power

Apparent power is the vector sum of active and reactive power, and is the product of the RMS values of voltage and current over the fundamental period.

What is Power Factor?

The power factor of an AC power system is defined as the ratio of the active power absorbed by the load to the apparent power flowing in the circuit, and is a dimensionless number in the range of −1 to 1. For an induction motor at full load, power factor is typically in the range 0.85 to 0.9.

What is Fundamental Frequency?

The fundamental frequency, often referred to simply as the fundamental, is defined as the lowest frequency of a periodic waveform.

What are Harmonics?

In an electric power system, a harmonic of a voltage or current waveform is a sinusoidal wave whose frequency is an integer multiple of the fundamental frequency. Harmonic frequencies are produced by the action of non-linear loads such as rectifiers, discharge lighting or saturated electric machines.

The effects of harmonics on electric systems are adverse, with effects including increased heating due to iron and copper losses, and higher audible noise emission.

What is Electrical Energy?

Electrical energy is the product of power multiplied by the length of time it was consumed. So if we know how much power, in Watts is being consumed and the time, in seconds for which it is used, we can find the total energy used.

What is Mechanical Power?

Shaft Power is the mechanical power transmitted from one rotating element of a vehicle, ship, and all types of machinery to another and is represented as Wshaft = 2*pi**τ or shaft power (W) = 2*pi*Revolutions per second (RPM/60)*Torque (Nm).

What is Advanced Power Analysis?

As well as calculating electrical power on 1 or more phases, mechanical power and energy, advanced power analysis using the following analysis techniques is also available with the Dewetron power analyser line:

  • Inverter, electrical machine (motor)  and total efficiency calculation
  • Speed-torque efficiency mapping
  • Harmonics and FFT data
  • DQ analysis (Park-Clarke transformation)
  • Drive cycle power and energy measurement, e.g. WLTP
  • Synchronised vibration and sound measurement
  • Digital interface – CAN, EtherCAT, Ethernet